This invention relates to improvements in an assembly for taking up and paying out flexible line, such as flexible hydraulic line. More particularly, the take-up assembly is specially designed for mounting on the mast of a lift truck such that the flexible line extends between the mast and the vertically reciprocating load carriage of the lift truck, upon which is mounted a powered load-handling attachment such as a clamp or side shifter.
Usually the moving parts of a lift truck load-handling attachment are powered by double-acting hydraulic cylinders, with respect to which hydraulic fluid must be simultaneously supplied and exhausted during operation. Such supply and exhaust of fluid is provided through a pair of flexible hydraulic lines extending to the lift truck carriage from a rotary reel of the take-up assembly, such reel in turn being connected through a rotary fluid coupling and through a further pair of hydraulic lines to the control valves of the hydraulic system of the lift truck. In order to accommodate the substantial vertical range of motion of the lift truck carriage and its associated load-handling attachment, the reel of the take-up assembly normally has sufficient storage capacity to permit paying out of the line to the limits of vertical travel of the load carriage, and is spring-loaded so as to impose a tension on the line to prevent slack and provide torque for rewinding of the line as the carriage moves closer to the take-up assembly.
The primary design objectives of lift-truck take-up assemblies have included serviceability, durability and compatibility with respect to the lift truck. With respect to serviceability, substantial design effort has been expended in the past to faciliate servicing and repair of take-up assemblies and their related flexible lines while mounted on the lift truck without requiring excessive disassembly. In this regard, reference is made particularly to U.S. Pat. Nos. 3,552,425 and 3,782,409, both of which are directed to the solution of certain problems relating to serviceability. A drawback of these designs however is that removal of the outer flange of the reel, which is particularly susceptible to damage and the need for replacement because of its exposed location, necessarily also results in removal of a substantial portion of the line-supporting hub of the reel, such that removal of the outer flange leaves a major portion of the wound line unsupported. This makes it difficult to retain the wound line in place when replacing the outer flange and, unless the line is removed from the reel, the unsupported coils can become a hindrance during servicing and reassembly.
A number of other take-up assemblies have been marketed which permit removal of the outer flange while retaining the entire line-supporting hub in place in its entirety. Although these assemblies, specifically those manufactured by Kaup and Tecalemit, retain the entirety of the hub in its line-supporting relation to the wound line despite removal of the outer flange, the retention of the hub in its entirety hinders the serviceability of other parts of the reel, particularly the line connectors located within the hub.
Previous take-up assemblies have different sets of connectors detachably connecting the flanges to the hub, and the retracting spring assembly to the hub, respectively. This is partially advantageous because it permits the removal of the outer flange of the reel without disrupting the highly-wound spring assembly. On the other hand, servicing of the spring assembly is rendered more difficult by the need for access to and manipulation of two separate sets of connectors for servicing the spring assembly.
A major problem with respect to the durability of hydraulic hose take-up devices is the durability of their seal structure for preventing leakage of the highly-pressurized hydraulic fluid which must be conducted through a rotary fluid coupling in the take-up assembly. Since lift trucks often operate in wet or dusty environments, contaminants in the form of water and dust can ultimately invade the close-tolerance seal structure of the rotary coupling and, by corrosion and wear, cause the onset of leakage. Attempts to use compression-type external seals to block such contamination result in excessive frictional resistance to rotation of the reel. Conversely, non-compression-type felt seals are unable to prevent moisture contamination of the internal hydraulic seal structure.
Compatibility of take-up assemblies with respect to lift trucks has become an increasing problem as lift truck designs have changed. For example the hydraulic systems of different lift trucks are capable of imposing different hydraulic pressures on the take-up assembly, fluid lines and load-handling attachment. If the pressure is excessive it can cause leakage in the load-handling attachment or damage to the fluid lines.
Another problem involving both durability and compatibility has developed with respect to the fluid coupling by which the forward ends of the fluid lines extending from the take-up assembly are connected to the lift truck load carriage. Conventionally such fluid coupling has employed a swivel structure as shown in U.S. Pat. No. 3,552,425 for permitting the fluid lines to assume either an upwardly-pivoted attitude when the carriage is lowered or a downwardly-pivoted attitude when the carriage is raised above the elevation of the take-up assembly. Such swivel fluid couplings are susceptible to leakage for the same reasons discussed previously with respect to the rotary fluid coupling of the take-up assembly. Moreover such swivel couplings sometimes protrude rearwardly from the load carriage a sufficient distance to interfere with other portions of the lift truck when the load carriage reciprocates vertically. Such interference principally occurs with respect to those lift trucks where the pistons of the mast's hydraulic tilt cylinders are attached to the sides of the mast at a relatively forward location. U.S. Pat. No. 2,975,807 shows a type of fluid line coupling between relatively movable parts which dispenses with the need for a swivel coupling. However, such coupling lacks the serviceability required for lift truck applications where fluid lines are highly suseptible to wear and other damage and require relatively frequent replacement without the expenditure of substantial time and effort.
A further problem involving compatibility of take-up assemblies with respect to lift trucks has been the requirement that some take-up assemblies, because of space constraints on the truck, must be mounted on the left side of the mast while others must be mounted on the right side. Unfortunately right side and left side take-up assemblies are not easily interchangeable, primarily because the helical retracting spring assemblies of the great majority of line take-up assemblies do not have reversible springs for permitting the take-up assembly to be mounted on either side of the mast. However the aforementioned Tecalemit take-up assembly is equipped with a reversible spring which is removably mounted within the spring housing such that, if the spring housing is detached from the remainder of the take-up assembly, the spring may be removed therefrom, inverted and replaced in a reverse configuration. In order to render the heavy, wound helical spring removable from its spring housing without permitting it to become dislodged from its helical configuration thereby endangering those around it, it must be restrained in some manner during the removal and replacement procedure. In the aforementioned Tecalemit take-up assembly such restraint is provided by a band surrounding the perimeter of the spring, such band having a pair of generally square, spring-enclosing shrouds spot-welded at their corners to each side of the band. The outer end of the Tecalemit spring is removably connected to the spring housing by means of a loop positioned interior of the restraining band which slidably engages an anchoring post protruding from the interior of the spring housing adjacent its perimeter, such loop being selectively slidable onto and off of the anchoring post in either of the spring's two reversed positions. The primary problem with this arrangement is that the spring restraint structure and spring anchoring post require a substantial annular, peripheral clearance between the exterior of the spring and the interior of the spring housing, thereby increasing the diameter of the spring housing substantially. Most line take-up assemblies are mounted on the mast with the outside of the spring housing located directly behind an outwardly-protruding flange of the mast as close thereto as possible, so as to minimize both the transverse protrusion and the rearward protrusion of the line take-up assembly. Minimizing transverse protrusion is necessary to prevent damage to the take-up assembly when the truck operates in close quarters, while minimizing rearward protrusion is necessary to prevent the take-up assembly from striking the truck's overhead guard upon rearward tilt of the mast. Any substantial increase in the diameter of the spring housing therefore can create a disadvantage in compatibly mounting the take-up assembly on the mast, depending on the design of the lift truck.